1. Field of the Invention
The present invention relates to a method for production of L-phenylalanine by recombinant Escherichia coli (E. coli). More particularly, the present invention relates to a novel E. coli containing a gene for the production of L-phenylalanine and a process for the production of L-phenylalanine by use of the novel microbe.
2. Description of the Prior Art
L-phenylalanine is a kind of essential amino acid and can be used for the synthetic production of ASPARTAME.RTM., a sweetening agent. There are many known methods for production of L-phenylalanine by use of microbes. For example, Japanese Kokai Nos. 37-6345 and 60-160,890 disclose a method for production of L-phenylalanine by use of Brevibacterium or Corynebacterium sp. which require tyrosine. Japanese Kokai 55-165,797 discloses a similar method by use of E. coli which requires tyrosine and which is resistant against tryptophan analogues. However, such prior art processes are not particularly suited for L-phenylalanine production on an industrial scale. Furthermore, these processes produce low yields of L-phenylalanine.
Accordingly, it is known that a prior process for manufacturing a product is to amplify copy numbers of a gene which codes for a rate-limiting enzyme in a specific process by genetic engineering techniques. However, in many cases over expression of a gene in a cell leads to deletion of the gene in a plasmid or lysis of a cell which causes the cell to die. There are many methods which properly control the expression of the plasmid. For example, an inducer like IPTG (isopropyl thio-galactoside) was used in the lac operator system to control lac operon and alkaline phosphatase gene (refer to Itakma, A. et al, Science, 198, 1056, (1977), Miyanohava, A. et al; Proc. Natl. Acad. Sci. U.S.A., 80, 1 (1983)).
Also, there is a temperatupe shift method which uses the repressor cI 857 of a phage. Normally, under 37.degree. C. the repressor is active and inhibits the operator so that transcription does not occur, but at a temperature higher than 37.degree. C., the repressor becomes inactive and no longer inhibits the operator so that the gene under control of repressor is expressed.